Analysis of the spatial and temporal distribution of Ebola cases in Bong County, Liberia: Implications for the role of general Community Health Volunteers in public health surveillance and response Open Access
Marum, Paul Christopher (2016)
Abstract
Background: The Liberian Ministry of Health reported 10,866 cases and 4,806 Ebola related deaths in the epidemic of 2014-15. An extensive system of community health workers served rural populations to convey information on symptoms, transmission risks and treatment for Ebola.
Methods: Geographic coordinates were recorded via GPS for all 39 health facilities in Bong County. Participatory mapping was conducted with the supervisors of general Community Health Volunteers (gCHVs) to identify and geolocate the villages where the 525 gCHVs reside. These data and other map sources were used to geolocate Ebola cases listed in Bong County records.
Results and Findings: By mid-2015, Bong County had achieved good coverage of gCHVs in all health districts. Of the 171 confirmed and probable Ebola cases, 156 were geolocated. Almost all cases (170/171) occurred between July and December 2014; cases living within 5 kilometers of a healthcare facility (HCF) displayed a typical epidemiologic curve with the majority occurring in August and September. Cases living 5 or more kilometers from a HCF primarily occurred later, from October to December, with three large clusters in rural communities. Hospitalization rates increased over time. The overall case fatality rate (CFR) in Liberia was 45%; in Bong County CFR was 41%; differences in CFR were minimal comparing hospitalization rates and distance from HCF in Bong County.
Discussion: The significant delay of Ebola incidence in more rural areas relative to the early peak in more urban areas suggests an initial protective effect of rural isolation. However, there remained significant danger of poorly controlled outbreaks in rural communities. The three major clusters in Bong County, all in more rural communities, highlighted the risk of rapid local transmission in these populations. Community health workers, including gCHVs, represent an important resource for rural disease control.
Future Directions: These findings reinforce the need for rural community public health interventions to prevent and control infectious diseases. Additional training of gCHVs in disease surveillance and community level infection control measures may empower gCHVs, and the rural populations they serve, to detect and respond to future outbreaks.
Table of Contents
Introduction .............. 1
Background: Ebola Epidemic in West Africa .............. 2
Lessons Learned from previous epidemics regarding control of Ebola .............. 3
Ebola Outbreak in Liberia .............. 4
Geographic and institutional factors affecting response to public health problems .............. 6
Community Health Workers and Response to Public Health Problems .............. 6
Distance from Health Facilities and Use of Health Services .............. 9
GIS in public health and epidemiology .............. 10
GIS as a tool in the Ebola response .............. 11
Bong County, Liberia: Background and Ebola epidemic ..............12
Health Infrastructure in Bong County .............. 12
General Community Health Volunteers and Community Responses to the Ebola Epidemic in Bong County .............. 14
Project Background .............. 16
Request for GIS assistance on Health infrastructure and gCHVs .............. 18
Research goal and aims .............. 18
Specific Aims of the research .............. 18
Methods .............. 19
Fieldwork and Data Sources .............. 19
Mapping of Bong County and Health Care Facilities .............. 20
Mapping of gCHVs .............. 21
Participatory mapping .............. 22
Mapping of Confirmed and Probable Ebola Cases .............. 24
Methods to Calculate Case Fatality Rates .............. 26
Findings related to the Distribution of Health Resources .............. 26
Distribution of Health Districts, Health Care Facilities and Population.............. 26
General community health volunteers.............. 27
Findings related to the Ebola Outbreak in Bong County .............. 27
Distribution by Week of Onset of symptoms.............. 27
Hospitalization of confirmed and probable Ebola cases.............. 29
Case Fatality Rates in Bong County.............. 30
Limitations .............. 30
Definition of Cases: .............. 30
Inconsistencies in case listings: .............. 31
Missing Data.............. 31
Mapping of Ebola Cases: .............. 31
General Community Health Volunteers (gCHVs).............. 32
Discussion.............. 33
References.............. 36
Tables .............. 39
Table 1: Population, Number of Health Facilities and gCHVs by Health District .............. 39
Table 2: Case fatality rates by hospitalization, isolation, and time. .............. 40
Figures.............. 41
Figure 1: Map of Counties in Liberia .............. 41
Figure 2: Map of administrative districts in Bong County showing Towns, Villages and major roads .............. 42
Figure 3: Decision Tree for inclusion or exclusion of possible Ebola cases .............. 43
Figure 4: Map of Health Care Facilities in Bong County showing the Health Districts .............. 44
Figure 5: Map of gCHVs and Supervising HCF in Bong County .............. 45
Figure 6: Histogram of Ebola cases by date of symptom onset .............. 46
Figure 7: Density plot of Ebola cases by date of symptom onset .............. 47
Figure 8: Histogram of Ebola cases by date of symptom onset and case classification .............. 48
Figure 9: Scatter plot of Ebola cases by symptom onset and distance from HCF .............. 49
Figure 10: Density Plot of Ebola cases by symptom onset and distance from HCF .............. 50
Figure 11: Histogram of Ebola cases by date of symptom onset and hospitalization .............. 51
Figure 12: Distribution of hospitalization rates with comparison by access to HCF .............. 52
Appendix: Definition of Ebola Virus Disease Cluster and/or outbreak .............. 53
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